Joule Thief circuit. CL have changed something in the simulator because this used to run with the sim set up as. Now, it does not show the exponential rise of V1 and does not start oscillating unless...

V1 (vcc) has exponential ramped startup to kick-start oscillation. XFRMR1 forms a centre tapped inductor However, CL takes a long time to run the simulation. Simulate > Time Domain > Run Time-Domain...